Reactor cleaning apparatus

ABSTRACT

In a reactor cleaning apparatus  1  which cleans an inner wall surface  72  of a reactor  70  which generates polycrystalline silicon, a bell jar of the reactor  70  has a dual structure, a through hole  11  is formed along a vertical direction at a central portion of a substantially disc-like tray  10  placed in a horizontal state, a flange portion  13  in which an opening edge of the reactor  70  is placed is formed at an outer peripheral portion of the tray  10 , a shaft  20  is provided through the through hole  11  of the tray  10  so as to be rotatable and movable in the vertical direction, a nozzle device  50  which sprays a cleaning water at high pressure in three-dimensional directions is provided at an upper end of the shaft  20 , a drive mechanism  30  which rotates the shaft  20  and moves the shaft in the vertical direction is provided at a base end of the shaft  20 , and steam piping  62  capable of supplying the steam within the bell jar of the reactor  70  is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reactor cleaning apparatus whichcleans an inner wall surface of a polycrystalline silicon reactor to beused when producing polycrystalline silicon using the Siemens method.

Priority is claimed on Japanese Patent Application No. 2008-014967,filed Jan. 25, 2008, the content of which is incorporated herein byreference.

2. Description of Related Art

The Siemens method is known as a method of producing high-puritypolycrystalline silicon to be used as a semiconductor material. ThisSiemens method is a production method of supplying a source gas which isa mixed gas of chlorosilane and hydrogens into contact with a heatedsilicon seed rod, and depositing the polycrystalline silicon which isgenerated by the thermal decomposition and hydrogen reducing reaction ofa source gas, on the surface of the seed rod. As an apparatus whichcarries out this production method, a polycrystalline silicon reactor inwhich many silicon seed rods are erected is used.

When polycrystalline silicon is produced in this polycrystalline siliconreactor, chlorosilane polymers which are generated as a by-product atthe time of the thermal decomposition and hydrogen reducing reaction arecondensed and adhered on cooled inner wall surface of the reactor. Inorder to remove the deposited polycrystalline silicon rods, the reactorhas to be opened to the atmosphere. On this occasion, chlorosilanepolymer and moisture in the atmosphere undergo hydrolysis, hydrogenchloride is generated. The hydrogen chloride erodes the inner surface ofthe reactor and deteriorates the working environment, and acontamination source is generated the polycrystalline silicon products.Additionally, in the situation that chlorosilane adheres to the bell jarwhich is a member of the reaction vessel and a bell-shaped object havinglower opening edge, reflectivity of inner wall surface of the reactordecreases, the radiation heat from heated silicon rods is not reflected,and the efficiency in the use of electricity decreases. Therefore, inorder to generate effectively the highly-pure polycrystalline silicon,when once a reaction is finished, it is necessary to remove the depositsbefore the next reaction. Therefore, for example, in Japanese PatentUnexamined Publication No. 56-114815, a method of supplying steam insidea wall of a polycrystalline silicon reactor to heat the inner wallsurface of the reactor, introducing an humidified gas into thepolycrystalline silicon reactor to hydrolyze chlorosilane polymeradhered to the inner wall surface of the reactor, loading a nozzle intothe reactor to spray a high-speed jet stream of the inert gas to theinner wall surface and removing the deposits on the inner wall surfaceof the reactor is suggested. Additionally, the method of removing thedeposits by blasting of CO₂ pellets to the inner wall surface of thereactor is described, for example, in Japanese Patent Publication No.3167191.

SUMMARY OF THE INVENTION

Meanwhile, in the cleaning method described above, it is difficult tospray the high-speed jet stream uniformly throughout the inner wallsurface of the reactor having irregularities, and it is impossible toperfectly remove the deposits. Additionally, in the method of using CO₂pellets described Japanese Patent Publication No. 3167191, hydrolysis ofthe silicon deposits is not proceeded, hydrogen chloride might begenerated when the reactor is opened.

The present invention was made in view of such a problem, and an objectthereof is to provide a reactor cleaning apparatus capable of easily andreliably removing deposits and cleaning water of an inner wall surfacein a polycrystalline silicon reactor.

In order to solve the above problem, the invention suggests thefollowing means.

That is, in the prevent invention, there is provided a apparatus forcleaning an inner surface of a bell jar that has a dual structure in areactor generating a polycrystalline silicon, a drainage hole is formedin a substantially disc-like tray placed in a horizontal state, a flangeportion on which an opening edge of the wall bottom of the reactor isplaced is formed at an outer peripheral portion of the tray, a shaft isprovided through the through hole of the tray so as to be rotatable andmovable in the vertical direction, a nozzle device which sprays acleaning water at high pressure in three-dimensional directions isprovided at an upper end of the shaft, a drive mechanism which rotatesthe shaft and move the shaft in the vertical direction is provided atthe shaft, and steam piping capable of supplying the steam within thebell jar of the reactor is provided between the outer wall and the innerwall.

When the inner wall surface of the reactor is cleaned by this reactorcleaning apparatus, the reactor is placed on the disc-like tray suchthat the lower opening edge of the reactor abuts on the flange portionof the outer peripheral portion of the tray from the above.Additionally, the shaft having the nozzle device at its upper end isprovided at the central portion of the tray in the vertical direction,and the shaft rotates and moves in the vertical direction by the drivemechanism provided at the base end of the shaft. The nozzle deviceprovided at the upper end of the shaft in this way sprays a cleaningwater at high pressure in three-dimensional directions, in accordancewith up-down movement of the shaft. Since this makes it possible tospray the cleaning water at high pressure in various directionsthree-dimensionally from an upper portion of the inner wall surface ofthe reactor to a lower portion thereof, it becomes possible to directlyspray the cleaning water uniformly throughout an inner wall surface ofthe reactor. Additionally, using the cleaning water becomes possible toprogress hydrolysis of the deposits and to remove as chemically stablesilica.

In addition, although corrosive gas, such as hydrogen chloride, isgenerated during cleaning, the space inside the reactor is in asubstantially sealed state except for the cleaning liquid dischargehole, and the corrosive gas is all discharged to the outside of thesystem from the discharge hole. Accordingly, the deterioration of theexternal atmosphere by the hydrogen chloride can be prevented, and theworking environment for producing high-quality polycrystalline siliconcan be maintained.

Moreover, steam is supplied into the dual structure of the bell jar ofthe reactor. Thus, a cleaning water which remains inside the reactorafter spraying can be evaporated and removed reliably and efficiently,and the inside of the reactor can be kept at a clean level wherehigh-quality polycrystalline silicon can be produced.

Additionally, in the reactor cleaning apparatus according to the presentinvention, wherein the shaft has a feed screw formed on the outerperipheral portion, the tray is provided with a fixed nut which isscrewed to the feed screw and guides the shaft upward and downward inaccordance with rotation of the shaft, and the drive mechanism isprovided with a pulley to rotate by a power source thereof, and in whichthe shaft is inserted in a central portion of the pulley and providedwith a spline groove and a spline ridge, which allow the shaft and thepulley to fit thereto so as to be slidable in the length direction,between the inner peripheral surface of the pulley and the outerperipheral surface of the shaft.

Since the spline ridge of the shaft which fits to the spline ridge ofthe pulley, the shaft which fits to the pulley is also rotated whenpower is transmitted to the pulley by the power source. At this time,since the shaft fits to the pulley so as to be slidable in the lengthdirection of the shaft, the shaft is rotated reliably without losing thetransmission of power from the pulley to the shaft even if the feedscrew of the shaft is guided by the fixed nut and the shaft moves up anddown. Accordingly, since the shaft can be moved up and down while arotative force is reliably transmitted to the shaft, the nozzle deviceprovided at the upper end of the shaft is able to spray the cleaningwater effectively over the upper and lower portions of the inner wallsurface of the reactor.

Moreover, in the reactor cleaning apparatus according to the invention,an upper surface of the tray is inclined so as to have a descendinggradient toward the drainage hole. Thereby, the cleaning waste liquidwhich is sprayed to the inner wall surface of the reactor and isaccommodated in the tray is easily guided to the drainage hole.Therefore, the cleaning waste liquid can be easily drained aftercleaning.

Additionally, according to the method for cleaning an inner surface of abell jar of the reactor having a dual structure which generatespolycrystalline silicon, the method comprising the steps of: providing alower opening edge of the bell jar on the substantially disc-like tray;rotating and moving the shaft provided in a central portion of the trayin the vertical direction, and cleaning an inner peripheral surface ofthe bell jar by spraying a cleaning water at high pressure inthree-dimensional directions with the nozzle device provided at an upperend of the shaft; draining the wasted cleaning water from the drainagehole formed in the tray; supplying the steam between an outer wall andan inner wall of the bell jar; and drying the inner peripheral surfaceof the bell jar.

According to the reactor cleaning apparatus related to the invention,the cleaning water can be sprayed at high pressure three-dimensionallyin various directions from an upper portion of the inner wall surface ofthe reactor to a lower portion thereof, and it becomes possible todirectly spray the cleaning water uniformly throughout inner wallsurface of the reactor. Additionally, since corrosive gas, such ashydrogen chloride is discharged to the outside of the system from thedischarge hole, and the cleaning water makes to progress hydrolysis ofthe deposits and to remove the deposits as chemically stable silica, thetreatment of the reactor after the cleaning is safe. In addition, sincesteam can be supplied into the bell jar of the reactor, remainingcleaning water is can be removed efficiently and reliably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a reactor cleaningapparatus related to this embodiment.

FIG. 2 is a plan view of a tray of the reactor cleaning apparatusrelated to this embodiment.

FIG. 3 is an A-A sectional view in FIG. 1.

FIG. 4 is a B-B sectional view in FIG. 1.

FIG. 5 is an enlarged view of a nozzle device of the reactor cleaningapparatus related to this embodiment.

FIG. 6 is an A-A sectional view of a deformation example of a splinejoint portion of pulley and shaft in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a reactor cleaning apparatus that is an embodiment of theinvention will be described in detail with reference to the drawings.FIG. 1 is a schematic configuration diagram of a reactor cleaningapparatus related to this embodiment, FIG. 2 is a plan view of a tray ofthe reactor cleaning apparatus related to this embodiment, FIG. 3 is anA-A sectional view in FIG. 1, FIG. 4 is a B-B sectional view in FIG. 1,and FIG. 5 is an enlarged view of a nozzle device of the reactorcleaning apparatus related to this embodiment. As shown in FIG. 1, thereactor cleaning apparatus 1 related to this embodiment generallyincludes a tray 10, a shaft 20, a drive mechanism 30, a fixed nut 40,and a nozzle device 50.

The tray 10 has a substantially disc-like shape, and is placed such thata bottom surface of an outer peripheral portion of the tray 10 issupported by a strut 61 suitably erected on a floor portion 60. As shownin FIG. 2, a through hole 11 is provided at a central portion of thetray 10 in plan view so as to penetrate the tray in a verticaldirection, and a cleaning water discharge hole 12 is provided in middleposition of radial direction of the tray 10. The upper surface 10 a ofthe tray 10 is formed in an inclined manner so as to have a descendinggradient toward the cleaning water discharge hole 12.

Additionally, a rubber packing 71 abuts is provided on as an outerperipheral portion of the tray 10 (a flange portion 13). This rubberpacking 71 is contacts at the lower opening edge of a bell jar of areactor 70 to be cleaned. The bell jar 70 is firmly fixed on the tray 10as, for example, bolting or the like is performed by a plurality of(twelve in this embodiment) detent portions 13 a provided at intervalsin the flange portion 13.

Additionally, as shown in FIG. 1, the hanging bell-shaped bell jar 70has a dual structure which consists of outer wall 70A and inner wall70B, and the inside of the reactor is hollowed. Thus, steam is suppliedinto the dual structure of the bell jar 70 of the reactor via a steamsupply channel 63 from steam piping 62 provided annularly around thestrut 61.

The shaft 20 extends along a vertical axis O so as to pass through thefloor portion 60 and pass through the through hole 11 of theabove-mentioned tray 10, and is provided so as to be rotatable aroundthe vertical axis O. Additionally, a cleaning water supply channel 21 ispierced along the vertical axis O in the shaft 20. Thus, a cleaningwater for cleaning an inner wall surface 72 of the bell jar 70 issupplied to the cleaning water supply channel 21 from a cleaning watersupply pipe 23 connected to a cleaning water supply source (not shown)via a rotary joint 22 placed at a lower end portion of the shaft 20.Purified water or ultrapure water is used as the cleaning water.

Moreover, a feed screw 25 is formed at an outer peripheral portion ofthe shaft 20 which is notched in an L shape along the vertical axis Osuch that four spots of the outer peripheral surface thereof formed withthe feed screw 25 form spline ridge and which is formed in a cross shapein a horizontal cross-section as shown in FIG. 3. Accordingly, the feedscrew 25 is arranged only at the ends of the cross in the horizontalcross-section of the shaft 20.

The drive mechanism 30 includes a power source 31 composed of a motor, areducer, etc; a pulley 32 having a disc shape; and a transmission belt33 which transmits the rotation of the power source 31 to the pulley 32.Additionally, as shown in FIG. 3, a cross-shaped hole 32 a which has across shape in plan view is opened in the middle of the pulley 32 as aspline groove. The outer peripheral surface of the above-mentioned shaft20 fits into the cross-shaped hole 32 a, and the rotation of the pulley32 is transmitted to the shaft 20.

In addition, the cross-shaped hole 32 a of the pulley 32 and the shaft20 are fitted to each other so as to be slidable in the verticaldirection. Accordingly, while the rotation of the pulley 32 istransmitted to the shaft 20, the shaft 20 is adapted to be able to movein the vertical direction with respect to the pulley 32.

The fixed nut 40 is a member which has a cylindrical shape and is fixedin accordance with the tray 12 onto a fixed base 41 provided below thetray 10 so as to pass through the through hole 11 of the tray 10. Theinside of the fixed nut is formed with an internal thread 42 whichextends along the vertical axis O. As shown in FIG. 4, the feed screw 25of the shaft 20 is screwed to the internal thread 42 of the fixed nut40, and the shaft 20 rotated in the direction of arrow T by the drivemechanism 30 moves upward such that the feed screw 25 is guided by theinternal thread 42 of the fixed nut 40. On the other hand, when theshaft 20 is rotated in a direction opposite to the direction of arrow T,it moves downward. Additionally, bellows 64 which extend to verticaldirection is provided at an outer periphery of the fixed nut 40 so as tosurround the fixed nut 40 and the shaft 20 and to seal the through-hole11. In accordance with the up-down movement of the shaft 20, the bellows64 is also expanded and contracted so as to surround the shaft 20constantly.

The nozzle device 50 is provided at an upper end of the shaft 20. Thenozzle device is supplied with cleaning water from the cleaning watersupply channel 21 of the shaft 20, and sprays the cleaning water at highpressure while being rotated in these directions. Specifically, as shownin FIG. 5, while a rotary housing 52 provided so as to protrude in thehorizontal direction from the nozzle device body 51 is rotated in thedirection of arrow U around a horizontal axis P, a nozzle device body 51is rotated around the vertical axis O. This makes it possible to spraythe cleaning water three-dimensionally in various directions from twonozzles 53 disposed on the rotary housing 52 at intervals of 180° so asto face a direction vertical to the horizontal axis P.

In addition, the driving of the nozzle device body 51 can have variousmethods. The cleaning water supplied from the cleaning water supplychannel 21 turns, for example, an impeller (not shown) which is providedin the nozzle device body 51, the rotary housing 52 is rotated in thedirection of arrow U around the horizontal axis P by the torque thereof.The nozzle device body 51 may be rotated in the direction of arrow Taround the vertical axis O over a gear (not shown) by the torquethereof.

With the reactor cleaning apparatus 1 constructed as above, when theinner wall surface 72 of the reactor 70 is cleaned, the rubber packing71 abuts is provided on as an outer peripheral portion of the tray 10 (aflange portion 13). The rubber packing 71 is contacts at the loweropening edge of a bell jar of a reactor 70. In addition, drains pipes 65are connected to a drainage hole 12. Then, the shaft 20 rotated in thedirection of T around the vertical axis O by the drive mechanism 30 isguided and moved upward by the fixed nut 40. Thereby, the nozzle device50 attached the shaft 20 also moves upward as the rotation in thedirection T around the vertical axis O in a state where the nozzledevice faces the inner wall surface 72 of the reactor 70 placed abovethe tray 10.

Further, when the cleaning water is jetted, the nozzle device 50 rotatesin the direction of T around the vertical axis O. In addition to this,the rotary housing 52 is rotated in the direction U around thehorizontal axis P to spray the cleaning water at high pressure in thedirection vertical to the horizontal axis P from the nozzles 53 providedin the rotary housing 52. On the other hand, when the drive mechanism 30rotates the shaft 20 in the direction opposite to the direction T aroundthe vertical axis O, the shaft 20 moves downward. With this downwardmovement, the nozzle device 50 moves downward while spraying thecleaning water as mentioned above. Since this makes it possible to spraythe cleaning water at high pressure three-dimensionally in variousdirections from an upper portion of the inner wall surface 72 of thebell jar 70 to a lower portion thereof, it becomes possible to directlyspray the cleaning water uniformly throughout an inner wall surface 72of the reactor 70. This injection pressure of the cleaning water is from10 MPa to 25 MPa. This range of the injection pressure is capable ofeasily and reliably removing the deposits of the inner wall surface 72of the reactor 70.

At this time, steam is supplied into the dual structure of the bell jarof the bell jar 70. Thus, a cleaning water component which remainsinside the bell jar 70 after spraying can be evaporated and removedreliably and efficiently, and the inside of the bell jar 70 can be keptat a cleaning level where high-quality polycrystalline silicon can beproduced.

Additionally, the outer peripheral portion of the shaft 20 is notchedalong the vertical axis O so as to leave the feed screw 25 in a portionthereof, and the notched portion is formed in a cross shape in crosssection, and the shaft 20 fits into the cross-shaped hole 32 a of thepulley 32. Therefore, when the rotation of the power source 31 istransmitted to the pulley 32 by the transmission belt 33, the shaft 20which fits to the pulley 32 is also rotated. At this time, since theshaft 20 fits the pulley 32 so as to be slidable in the verticaldirection, the shaft 20 is rotated reliably without obstructing thetransmission of power from the pulley 32 to the shaft 20 even if thefeed screw 25 of the shaft 20 is guided by the fixed nut 40 and theshaft 20 moves up and down. Accordingly, since the shaft 20 can be movedup and down while a rotative force is reliably transmitted to the shaft,the nozzle device 50 provided at the upper end of the shaft 20 is ableto spray the cleaning water effectively over the upper and lowerportions of the inner wall surface 72 of the reactor 70.

Additionally, since the upper surface 10 a of the tray 10 is inclined soas to have a descending gradient toward the discharge hole 12, thecleaning water which has been sprayed to the inner wall surface 72 ofthe bell jar 70 and is accommodated in the tray 10 is easily guided tothe discharge hole 12. Therefore, the cleaning water can be easilyremoved after cleaning.

Additionally, since the cleaning water is used, this makes it possibleto progress hydrolysis of the deposits and to remove as chemicallystable silica. If there are slightly residues on such as the bell jar70, it is harmless silica, and safe.

In addition, although corrosive gas, such as hydrogen chloride, isgenerated during cleaning, the space inside the bell jar 70 is in asubstantially sealed state except for the discharge hole 12, and thecorrosive gas is all discharged to the outside of the system through thedrains pipes 65 from the the discharge hole 12. Accordingly, thedeterioration of the external atmosphere by the hydrogen chloride can beprevented from, and the working environment for producing high-qualitypolycrystalline silicon can be maintained.

Although the reactor cleaning apparatus 1 that is the embodiment of theinvention has been described hitherto, the invention is not limitedthereto, and can be suitably changed without departing from thetechnical idea of the invention.

For example, in this embodiment, as the spline ridge of the outerperipheral portion of the shaft 20, the outer peripheral portion isnotched in an L shape along the vertical axis O such that four spots ofthe outer peripheral surface thereof form spline ridge, and is formed ina cross shape in a horizontal cross-section. However, the shape of theouter peripheral portion of the shape is not limited to the cross shapeso long as the spline ridge are formed in the length direction of theshaft 20.

For example, it may be the embodiment indicated in FIG. 6. As shown inFIG. 6, the shaft 80 has a cylindrically shape, one of the spline groove81 are formed in the length direction of the shaft 80 in a portion ofthe outer peripheral portion thereof, the pulley 82 is formed withspline ridge 84 fit the spline groove 81 in the inner peripheral portionof the circular hole 83 which is fully inserted the shaft 80. The splinegroove and spline ridge may be provided to fit between the shaft and thepulley.

Additionally, the feed screw 25 and spline ridge of the shaft 20 may beformed independently from each other. That is, in this embodiment, theshaft 20 is formed in a cross shape in cross-section as the splineridge, and the feed screw 25 is formed at ends of the cross. However, inthe shaft 20, the spot where spline ridge are formed and the spot wherethe feed screw 25 is formed may be separated.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

1. A reactor cleaning apparatus which cleans an inner wall surface of areactor which produces polycrystalline silicon, a bell jar of thereactor having a dual structure, the reactor cleaning apparatuscomprising: a substantially disc-like tray placed in a horizontal state;a drainage hole formed in the tray; a through hole formed along avertical direction in a central portion of the tray; a flange portion,at an outer peripheral portion of the tray, on which a lower openingedge of the bell jar is placed; a shaft provided through the throughhole of the tray so as to be rotatable around an axis and movable in thevertical direction; a nozzle device provided at an upper end of theshaft to spray a cleaning water at high pressure in three-dimensionaldirections; a drive mechanism provided to rotate the shaft and move theshaft in the vertical direction; and steam piping provided so as to becapable of supplying the steam within the bell jar.
 2. The reactorcleaning apparatus of claim 1, wherein the shaft has a feed screw formedon the outer peripheral portion, the tray is provided with a fixed nutwhich is screwed to the feed screw and guides the shaft upward anddownward in accordance with rotation of the shaft, and the drivemechanism is provided with a pulley to rotate by a power source thereof,and in which the shaft is inserted in a central portion of the pulleyand provided with a spline groove and a spline ridge, which allow theshaft and the pulley to fit thereto so as to be slidable in the lengthdirection, between the inner peripheral surface of the pulley and theouter peripheral surface of the shaft.
 3. The reactor cleaning apparatusof claim 1, wherein the tray is inclined so as to have a descendinggradient toward the drainage hole.
 4. The reactor cleaning apparatus ofclaim 2, wherein the tray is inclined so as to have a descendinggradient toward the drainage hole.